This invention relates to lubricating compositions, concentrates and greases containing the combination of an organic polysulfide and an overbased composition or a phosphorus or boron compound.
Polysulfides have been used to provide extreme pressure protection to lubricating compositions. However, polysulfides may lead to copper corrosion, seal compatibility, oxidation stability, and thermal stability problems. It is desirable to find a polysulfide which when used in combination with other additives provides good extreme pressure properties to lubricants without the above adverse effects.
This invention relates to a lubricating composition comprising a major amount of an oil of lubricating viscosity, (A) at least one organic polysulfide comprising at least about 90% dihydrocarbyl trisulfide, from about 0.1% up to about 8% dihydrocarbyl disulfide, and less than about 5% dihydrocarbyl higher polysulfides, and (B) at least one overbased metal composition, at least one phosphorus or boron compound, or mixtures of two or more thereof. The invention also relates to concentrates and greases containing the above combination. The invention also relates to methods of making the organic polysulfide.
The term xe2x80x9chydrocarbylxe2x80x9d includes hydrocarbon as well as substantially hydrocarbon groups. Substantially hydrocarbon describes groups which contain heteroatom substituents that do not alter the predominantly hydrocarbon nature of the substituent. Examples of hydrocarbyl groups include the following:
(1) hydrocarbon substituents, i.e., aliphatic (e.g., alkyl or alkenyl) and alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, aromatic-, aliphatic- and alicyclic-substituted aromatic substituents and the like as well as cyclic substituents wherein the ring is completed through another portion of the molecule (that is, for example, any two indicated substituents may together form an alicyclic radical);
(2) substituted hydrocarbon substituents, i.e., those substituents containing non-hydrocarbon groups which, in the context of this invention, do not alter the predominantly hydrocarbon nature of the substituent; those skilled in the art will be aware of such groups (e.g., halo (especially chloro and fluoro), hydroxy, mercapto, nitro, nitroso, sulfoxy, etc.);
(3) heteroatom substituents, i.e., substituents which will, while having a predominantly hydrocarbon character within the context of this invention, contain an atom other than carbon present in a ring or chain otherwise composed of carbon atoms (e.g., alkoxy or alkylthio). Suitable heteroatoms will be apparent to those of ordinary skill in the art and include, for example, sulfur, oxygen, nitrogen and such substituents as, e.g. pyridyl, furyl, thienyl, imidazolyl, etc.
In general, no more than about 2, preferably no more than one heteroatom substituent will be present for every ten carbon atoms in the hydrocarbyl group. Typically, there will be no such heteroatom substituents in the hydrocarbyl group. Therefore, the hydrocarbyl group is hydrocarbon.
The term reflux ratio refers to the ratio of the amount of material returned to the distillation apparatus to the amount of material removed from the distillation. For instance, a reflux ratio of 5:1 means that five parts of distillate are returned to the distillation apparatus for every one part removed from the apparatus.
As described above, the present invention relates to compositions containing (A) at least one polysulfide having specific proportions of sulfides in combination with (B) at least one overbased composition, at least one phosphorus or boron compound, or mixtures thereof. In one embodiment, the organic polysulfide (A) is present at concentrations in the range of about 0.1% to about 10% by weight, or from about 0.2% up to about 8%, or from about 0.3% up to about 7%, or from about 0.5% to about 5% by weight. Here, as well as elsewhere in the specification and claims, the range and ratio limits may be combined. In one embodiment, the overbased composition, the phosphorus or boron compound, or mixture thereof (B) is present in an amount from about 0.05% up to about 10%, or from about 0.08% up to about 8%, or from about 0.1% up to about 5% by weight.
The organic polysulfide is a mixture comprising at least about 90% dihydrocarbyl trisulfide, from about 0.1%, or from about 0.5% up to about 8% dihydrocarbyl disulfide, and less than about 5% dihydrocarbyl higher polysulfides. Higher polysulfides are defined as containing four or more sulfide linkages. In one embodiment, the amount of trisulfide is at least about 92%, or preferably at least about 93%. In another embodiment, the amount of dihydrocarbyl higher polysulfides is less than 4%, or preferably less than about 3%. In one embodiment, the dihydrocarbyl disulfide is present in an amount from about 0.1%, or from about 0.5% up to about 5%, or preferably from about 0.6% up to about 3%.
The sulfide analysis is performed on a Varian 6000 Gas Chromatograph and FID detector SP-4100 computing integrator. The Column is a 25 m. Megabore SGE BP-1. The temperature profile is 75xc2x0 C., hold 2 min., to 250xc2x0 C. at 6xc2x0 C./min. The helium flow is 6.0 ml/min plus make-up. The injection temperature is 200xc2x0 C. and the detector temperature is 260xc2x0 C. The injection size is 0.6, ul. References are the monosulfide, disulfide and trisulfide analogues to the sulfur composition for analysis. The references may be obtainied by fractionating the product to form sulfide fractions (S1, S2 and S3) to be used for analysis. The procedure for analysis is as follows. (1) An area % determination is run on each of the reference samples to determine its purity. (2) An area % determination is run on the sample to be tested to get a general idea of its composition. (3) A calibration blend is accurately weighed based on the area % results of the sample to be tested: then the internal standard toluene, is added to the blend in an amount equal to approximately one-half of the weight of the largest component. (This should give an area approximately the same as that of the largest component.) (4) The weights of each component (i.e., S-1, S-2 and S-3) are corrected by the % purity from step 1. (5) The calibration blend is run in triplicate using the corrected weights and then calculated, using the following formula, to reflect the multiple peaks in S-1 and S-2:       RF    =                            (                      concentration            ⁢                          xe2x80x83                        ⁢            of            ⁢                          xe2x80x83                        ⁢                          components              *                                )                          (                      total            ⁢                          xe2x80x83                        ⁢            area            ⁢                          xe2x80x83                        ⁢            of            ⁢                          xe2x80x83                        ⁢            peaks                    )                    ⁢                        (                      area            ⁢                          xe2x80x83                        ⁢            of            ⁢                          xe2x80x83                        ⁢            internal            ⁢                          xe2x80x83                        ⁢            standard                    )                          (                      concentration            ⁢                          xe2x80x83                        ⁢            of            ⁢                          xe2x80x83                        ⁢            internal            ⁢                                          xe2x80x83                            ⁢                              xe2x80x83                                      ⁢            standard                    )                                xe2x80x83        ⁢                                                      *                        ⁢                          xe2x80x83                        ⁢                          Adjusted  for  purity  of  the  standard  i.e.:  component  weight  times                                                                         percent  purity  equals  concentration  of  component.                              
(6) These response factors, plus the response factor for the single S-3 peak are used for determining weight percent results for the samples to be tested. (7) Results for S-1 and S-2 are adjusted to include all the peaks attributed to them. (8) Higher polysulfides are determined by difference using the following formula:
S-4=100%xe2x88x92(S-1+S-2+S-3+light ends)
Light ends are defined as any peaks eluded prior to the internal standard.
The organic polysulfide generally has hydrocarbyl groups each independently having from about 2 to about 30, preferably from about two to about 20, or from about 2 to about 12 carbon atoms. The hydrocarbyl groups may be aromatic or aliphatic, preferably aliphatic. In one embodiment, the hydrocarbyl groups are alkyl groups.
The organic polysulfides may be derived from an olefin or a mercaptan. The olefins, which may be sulfurized, contain at least one olefinic double bond, which is defined as a non-aromatic double bond. Olefins having from 2 up to about 30, or from about 3 up to about 16 (most often less than about 9) carbon atoms are particularly useful. Olefins having from 2 up to about 5, or from 2 up to about 4 carbon atoms are particularly useful. Isobutylene, propylene and their dimers, trimers and tetramers, and mixtures thereof are especially preferred olefins. Of these compounds, isobutylene and diisobutylene are particularly desirable.
The mercaptans used to make the polysulfide may be hydrocarbyl mercaptans, such as those represented by the formula Rxe2x80x94Sxe2x80x94H, wherein R is a hydrocarbyl group as defined above. In one embodiment, R is an alkyl, an alkenyl, cycloalkyl, or cycloalkenyl group. R may also be a haloalkyl, hydroxyalkyl, or hydroxyalkyl substituted (e.g. hydroxymethyl, hydroxyethyl, etc.) aliphatic groups. R generally contains from about 2 to about 30 carbon atoms, or from about 2 to about 24, or from about 3 to about 18 carbon atoms. Examples include butyl mercaptan, amyl mercaptan, hexyl mercaptan, octyl mercaptan, 6-hydroxymethyloctanethiol, nonyl mercaptan, decyl mercaptan, 10-amino-dodecanethiol, dodecyl mercaptan, 10-hydroxymethyl-tetradecanethiol, and tetradecyl mercaptan.
In one embodiment, the organic polysulfide may be prepared by reacting, optionally under superatmospheric pressure, one or more of the above olefins with a mixture of sulfur and hydrogen sulfide in the presence, or absence, of a catalyst, such as an alkyl amine catalyst, followed by removal of low boiling materials. The olefins which may be sulfurized, the sulfurized olefin, and methods of preparing the same are described in U.S. Pat. Nos. 4,119,549, 4,199,550, 4,191,659, and 4,344,854. The disclosure of these patents is hereby incorporated by reference for its description of the sulfurized olefins and preparation of the same. The polysulfide thus produced is fractionally distilled to form the organic polysulfide of the present invention. In one aspect, the fractional distillation occurs under subatmospheric pressure. Typically the distillation pressure is from about 1 to about 250, preferably from about 1 to about 100, or preferably from about 1 to about 25 mm Hg. A fractionation column such a Snyder fractionation column may be used. In one embodiment, the fractionation is carried out at a reflux ratio of from about 1:1 up to about 15:1, preferably from about 2:1 up to about 10:1, or preferably from about 3:1 up to about 8:1. The fraction distillation occurs at a temperature at which the sulfur composition which is being fractionated boils. Typically the fractional distillation occurs at a pot temperature from about 75xc2x0 C. to about 300xc2x0 C., or from about 90xc2x0 C. to about 200xc2x0 C.
The conditions of fractional distillation are determined by the sulfur composition being distilled. The present invention also relates to a method of making the organic polysulfide (A). The method involves fractional distillation of a sulfur composition. The method involves heating the sulfur composition to a temperature at which boiling occurs. The distillation system is brought to equilibrium and the distillation commences with a chosen reflux ratio (described above). The fractions obtained from the distillation are removed from the distillation apparatus. The amount of the desired fraction may be calculated by determining the proportion of sulfides. The desired fraction is obtained by maintaining accurate temperature control on the distillation system. The boiling fractions are removed at a specific vapor and temperature for that fraction. The reflux ratio is adjusted to maintain the temperature at which this fraction boils. After removal of the desired fraction, the fraction may be further filtered as desired.
In general, fractionation is carried out in a continuous or a batch process. In a continuous process the material to be fractionated is fed to a fractionating column. Parameters are controlled in the system such as feed flow, temperatures throughout the column, and the reflux ratio, etc., to separate the components in the feed into an overhead and bottoms stream. These parameters are adjusted to maintain the desired composition in the overhead and bottoms streams.
For a batch rocess, the material to be fractionated is charged to an agitated vessel and is heated to boiling temperatures. Once the material reaches the boiling point, the fractionation column system is brought to equilibrium. Subsequently, the desired reflux ratio is set. Collecton of the distillate is commenced, as described herein. The reflux ratio is incresed as is necessary to maintain the appropriate temperatures in the fractionating column system. As the distillation rate slows, the reflux ratio is increased until eventually the collection of the distillate stops. The different fractions are separated as the above process is repeated at higher temperatures.